Faculty Publications

Reply to Eells et al. (Daily Cranberry Prophylaxis to Prevent Recurrent Urinary Tract Infections May Be Beneficial in Some Populations of Women)

Document Type

Article

Journal/Book/Conference Title

Clinical Infectious Diseases

Volume

52

Issue

11

First Page

1394

Last Page

1395

Abstract

TO THE EDITOR—We appreciate the kind words of Eells et al [1] regarding our recent article describing results of a randomized, double-blind clinical trial of the effects of cranberry juice versus placebo juice in preventing urinary tract infection (UTI) among 319 otherwise healthy women [2]. We were puzzled, however, with their statements regarding the study power. Power is a function of the effect size, sample size, and variance. Given that we observed a greater number of UTIs among participants receiving cranberry juice, it would have required a substantially larger sample size than that suggested by Eells et al [1], to overcome the observed deficit and produce a positive result—even if the study had been designed for a 14% recurrence rate. Thus, it does not seem to us conservative to assume—as their letter implies—that had our trial been doubled in size we may have observed a beneficial effect of cranberry juice over placebo. We note also, that the published trials among similar populations [3, 4] had sample sizes that were less than half of that of our trial.

Department

Department of Biology

Original Publication Date

6-1-2011

DOI of published version

10.1093/cid/cir194

Link to Full Text

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